Apparatus for making pipe insulation

ABSTRACT

A roll forming apparatus used for rolling a material around a cylindrical core that comprises a core support, a roll support means, and a material supply means. The core support has an associated core rotation means for rotating the core about an axis at a controllable rate. The roll support means supports a plurality of forming rolls positioned to surround the core about the core rotation axis. The roll support means has a roll control means operable to both radially position the plurality of forming rolls relative to the core rotation axis so that they are equally spaced from the rotation axis. The material supply means is for supplying the selected material to the core at a material supply rate, and has an associated material supply control means for controlling the material supply rate.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 09/413,016,filed Oct. 7, 1999, now U.S. Pat. No. 6,364,649.

FIELD OF THE INVENTION

This invention relates to manufacturing pipe insulation and moreparticularly to an apparatus and method for making pipe insulation.

BACKGROUND OF THE INVENTION

In order to manufacture a cylindrical insulation product suitable forinsulating pipes, an insulating material such as mineral fibre is firstformed into a cylindrical shape. After the insulation product has beenformed, it is typically hardened in this shape by curing. After curing,it may be necessary or desirable to sand the exterior of the hardenedcylindrical product in order to provide a regular, smooth exterior.

U.S. Pat. No. 3,344,009 (Levecque) discloses an apparatus for forminghollow cylinders of resin-impregnated mineral mats suitable for use asinsulation for systems of pipes or conduits. The apparatus includes amandrel about which the mat is wrapped. The winding of the mat on themandrel is executed pneumatically, in that the hollow mandrel hasperforations on its surface, and the interior of the mandrel is placedunder reduced pressure. After the mat has been formed on the mandrel, itis ejected therefrom and travels through a heating compartment thatheats the mat to a sufficient temperature and for a sufficient period oftime to cure the mat.

Prior apparatus such as that disclosed by Levecque may suffer from anumber of disadvantages. Typically, the mineral fibre used forinsulation is somewhat resilient. If, as is typically the case, themineral fibre is no longer subjected to compression after forming, thenthere may be some expansion of the compressed mineral fibre beforecuring. The expanded mineral fibre will then be cured, resulting in aninsulation product that may be of lower density than desired. Further,it is very desirable that the insulation product have a hard and smoothinside core as well as uniform wall thickness and outside diameter, asthis greatly facilitates fitting the insulation on pipes. Theconcentricity and outside diameter are as important as the insidediameter of the pipe since segments are cut and rotated 180 degrees toform segmented elbows; if the insulation product is not concentric orthe outside diameter changes, then the inside diameter of each segmentwill not line up. Typically, however, the insulation is removed from theforming mandrel before being fully cured. Accordingly, some of theexpansion, which may well be uneven, may occur on the inner surface ofthe insulation product as well as the outer surface of the insulationproduct, resulting in a cured inside core that is less hard and smooththan the core was at the end of the forming stage of manufacture. Theinsulation product may also differ in thickness at different pointsalong its length as a result of differential expansion.

Prior apparatus for winding insulating ply around a cylindrical corehave been devised. U.S. Pat. No. 5,143,314 (Soikkeli), issued on Sep.1992, discloses such a prior apparatus in which an insulating materialis wound around the core and a movable endless belt is bent around boththe core and the insulating material in order to compress and form theinsulating material around the core.

Prior art apparatus such as the Soikkeli apparatus may suffer from anumber of disadvantages. For example, the movable endless belt used bySoikkeli to hold and compress the insulating material next to the coremay not provide equal pressure on the insulating material all the wayaround the core. Indeed, at some points, the mineral fibre may not becontacted by the endless belt at all, resulting in uneven thickness anddensity of the insulation material after forming. Further, in theSoikkeli apparatus the forming radius provided by the endless beltcannot be separately controlled; instead this forming radius isdetermined by the tension in the endless belt and the resistance of theinsulation product to compression. This, in turn, may make it moredifficult to produce high tolerance insulation product, especially whenforming low density outer layers of insulation. High toleranceinsulation product is desirable for, among other applications,fabricating segmented sections of insulation to fit curved pipe.

Thus, a method and apparatus for manufacturing pipe insulation in whichthe insulation is kept on the mandrel or core throughout both the curingstage and the forming stage, and in which the desired shape and densityof the insulation product can be retained throughout the forming stageand the curing stage, is desirable. Preferably, the apparatus formanufacturing pipe insulation would include a roll forming apparatusthat provides substantially uniform compression to all exposed portionsof the insulating material around its circumference. It is alsodesirable that the rolling apparatus be easily and precisely adjustableto accommodate changes in the diameter of the insulating material andcore. In order to integrate the forming of the insulation product withsubsequent stages of manufacture, such as curing and sanding, it isdesirable that the core with the formed insulating material wrappedthereround be easily transportable to the subsequent curing stage.

SUMMARY OF THE INVENTION

An object of an aspect of the present invention is to provide animproved insulation manufacturing apparatus.

In accordance with this aspect of the present invention there isprovided a roll forming apparatus for rolling a selected material arounda cylindrical core. The apparatus comprises a core support, a rollsupport means, and a material supply means. The core support is forsupporting the cylindrical core. The core support has an associated corerotation means for rotating the core about a core rotation axis at acontrollable rotation rate. The roll support means supports a pluralityof forming rolls positioned to surround the core about the core rotationaxis. The roll support means has a roll control means operable to bothradially position the plurality of forming rolls relative to the corerotation axis and to constrain the plurality of forming rolls to beequally spaced from the core rotation axis, in order to provideintegrated adjustment of the plurality of forming rolls to control aradial dimension of a substantially symmetrical forming space defined bythe plurality of forming rolls. The material supply means is forsupplying the selected material to the core at a material supply rate,and has an associated material supply control means for controlling thematerial supply rate.

In accordance with another aspect of the present invention there isprovided an apparatus for receiving a selected curable material and forretaining the selected curable material during a forming stage and acuring stage. The selected curable material is formed into a desiredconfiguration during the forming stage, and is heated during the curingstage to harden the selected material in the desired configuration. Theapparatus includes a core mounted for rotation about an axis ofrotation, a curing means for heating the selected curable material to atleast a curing temperature to harden the selected curable material inthe selected configuration, and a vacuum means in fluid communicationwith the fluid communication means. The core has an associated corerotation means for rotating the core about an axis of rotation, an outerpermeable surface for receiving and retaining the selected curablematerial, and a fluid communication means for receiving air flow fromthe outer permeable surface. The vacuum means is operable to draw aforming core air flow through the fluid communication means, the outerpermeable surface of the core and the selected curable material retainedon the core during forming of the selected curable material retained onthe core. The forming core air flow has a temperature below the curingtemperature. The vacuum means is also operable to draw a curing core airflow through the outer permeable surface and the fluid communicationmeans of the core and the selected curable material retained on the coreduring curing of the selected curable material retained on the core.

An object of another aspect of the present invention is to provide animproved insulation manufacturing method.

In accordance with this aspect of the present invention there isprovided a method of forming and curing a selected curable material in adesired configuration. The method comprises the steps of (a) supplyingthe selected curable material to the core, (b) forming the selectedcurable material retained on the core, and (c) curing the selectedcurable material retained on the core. During steps (a), (b) and (c),the method also comprises drawing a core air flow through a permeablesurface of a core and through the selected curable material on the coreto retain the selected curable material on the core and to compress theselected permeable material to the core. The core air flow has an airtemperature below a curing temperature of the selected curable materialduring steps (a) and (b).

A BRIEF DESCRIPTION OF THE DRAWINGS

A detailed description of the preferred embodiments of the invention isprovided herein below with reference to the following drawings, inwhich:

FIG. 1 in a perspective view illustrates a vacuum core and a coresupport of an insulation making apparatus in accordance with a preferredembodiment of the present invention;

FIG. 2 in a perspective view illustrates the vacuum core and the coresupport of the insulation making apparatus of FIG. 1 in which the coresupport has been partially cut-away to show a vacuum duct;

FIG. 3, in a sectional view, illustrates a roll forming apparatus of aninsulation making apparatus in accordance with a preferred embodiment ofthe present invention;

FIG. 4, in a sectional view, illustrates the roll forming apparatus ofFIG. 3 wherein the apparatus has been adjusted to roll a core wrappedwith insulating material;

FIG. 5, in a sectional view, illustrates, the roll forming apparatus ofFIG. 3 in which the apparatus has been adjusted to roll a core withinsulating material of small diameter;

FIG. 6, in a sectional view, illustrates a forming roll of the rollforming apparatus of FIG. 3;

FIG. 7, in a sectional view, illustrates the geometry of the rollforming apparatus of FIG. 3;

FIG. 8 in a perspective view illustrates a curing oven of the insulationmaking apparatus of FIG. 1;

FIG. 9 in a cut-away perspective view illustrates the curing oven ofFIG. 8;

FIG. 10 in a sectional view of FIG. 9, illustrates the curing oven ofFIGS. 8 and 9;

FIG. 11, in a plan view, illustrates a preferred layout of the pipeinsulation making apparatus in accordance with a preferred embodiment ofthe invention; and

FIGS. 12 to 15, in different cut-away plan views, illustrate differentportions of a duct network connected to the vacuum core of FIG. 1 andthe curing oven of FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Referring to FIG. 1, there is illustrated in a perspective view a coresupport 21 and a core 22 of a pipe insulation making apparatus inaccordance with a preferred embodiment of the present invention. Thecore 22 is supported by the core support 21 at a horizontal swivel joint38. The horizontal swivel joint 38 supports the core 22 at an elevatedand generally horizontal orientation, while permitting rotation of thecore 22 about an axis of rotation 28. The core support 21 includes arotary drive 44 having a drive pinion 46. In operation, the rotary drive44 rotates the drive pinion 46, which, in turn, rotates the coregear-ring 48 and the core 22.

In operation, mineral fibre or other selected curable material 24 issupplied to the core 22 by any suitable means such as a conveyor. Whilethe selected curable material 24 is being supplied to the core 22, thecore 22 rotates around the axis of rotation 28 thereby wrapping theselected curable material 24 around the core 22. The core 22 ispartially hollow, and a partial vacuum is maintained in the interior ofthe core 22 in order to provide suction through perforations 26 in thesurface of the core 22. Suction provided via the perforations 26 helpsto hold the selected curable material 24 on the core 22.

Referring to FIG. 2, there is illustrated the core 22 and the coresupport 21 of FIG. 1; the core support 21 as shown in FIG. 2 has beenpartially cut-away to reveal a vacuum duct 32. Vacuum duct 32 isconnected to the interior of core 22 at the horizontal swivel joint 38.The connection of the vacuum duct 32 and the interior of the core 22 issealed at the horizontal swivel joint 38 by a horizontal end seal 36 inorder to maintain the partial vacuum in the interior of the core 22while permitting rotation of the core 22 relative to the vacuum duct 32.Vacuum duct 32 is, in turn, connected to a vacuum exhaust duct 34. Thepartial vacuum inside the vacuum duct 32 and the core 22 is maintainedby a partial vacuum in vacuum exhaust duct 34. Vacuum exhaust duct 34and vacuum duct 32 are of relatively large diameter and have relativelysmooth inside walls in order to minimize any pressure drop and provideoptimal suction to the perforations 26 of core 22.

Core support 21 is mounted on a support platform 41 for pivoting aboutpivot axis 30. Vacuum exhaust duct 34 is connected to core support 21 bya vertical swivel joint 42 and the vacuum exhaust duct 34 does not pivotwith core support 21. The connection of the vacuum duct 32 and thevacuum exhaust duct 34 is maintained and sealed at the vertical swiveljoint 42 by vertical end seal 40 in order to maintain the partial vacuumin the vacuum duct 32 while permitting the vacuum duct 32 to turnrelative to the vacuum exhaust duct 34.

Referring to FIG. 3, there is illustrated in a sectional view a rollforming apparatus 50 of a pipe insulation making apparatus in accordancewith a preferred embodiment of the present invention. The roll formingapparatus 50 comprises forming rolls 54, support arms 56, support armpivot pins 68, and a roll forming apparatus frame 53. The roll formingapparatus 50 surrounds a core 22 that is mounted for rotation about anaxis of rotation 28. Each support arm 56 is pivotably secured to theroll forming apparatus frame 53 by a unique one of the support arm pivotpins 68. Each of the support arm pivot pins 68 is fixed to the rollforming apparatus frame 53 at a common fixed radial distance, shown asR_(f) in FIG. 7, from the axis of rotation 28. Each support arm 56supports a single forming roll 54 spaced a common fixed arm distance,shown as D_(f) in FIG. 7, from the support arm pivot pin 68 for suchsupport arm 56. The support arms 56 may pivot about their respectivesupport arm pivot pins 68 to change the spacing of the forming rolls 54from the axis of rotation 28.

The rotation arms 56 include two proximal support arms 56 a, twointermediate support arms 56 b and two distal support arms 56 c. Eachproximal support arm 56 a is adjacent to a different intermediatesupport arm 56 b, which intermediate support arm 56 b, is, in turn,adjacent to a different distal support arm 56 c. Accordingly, thesupport arms 56 can be divided into two groups of adjacent support arms56, each group comprising a proximal support arm 56 a, an intermediatesupport arm 56 b and a distal support arm 56 c. The roll formingapparatus 50 includes a plurality of rod linkages 62; each rod linkagelinks adjacent support arms 56 within a group such that the support arms56 in a group are constrained to pivot together by equal amounts abouttheir respective support arm pivot pins 68. Specifically, within eachgroup the distal support arm 56 c is linked by an associated rod linkage62 c to the intermediate support arm 56 b, and the intermediate supportarm 56 b is linked by an associated rod linkage 62 b to the proximalsupport arm 56 a.

The roll forming apparatus 50 includes two support arm drivers 90, eachof which is linked to a different proximal support arm 56 a. The supportarm drivers 90 are operable to pivot the proximal support arms 56 aabout their respective support arm pivot pins 68. Turning to FIG. 5,each of the support arm drivers 90 is linked to a slide block 92 by aseparate one of two driver linkages 96. The slide block 92 is driven bya servo-driven ball screw (not shown). The servo-driven ball screw movesthe slide block 92, thereby moving the drive linkages 96 together, andoperating the support arm drivers 90 together to pivot the proximalsupport arms 56 a together by equal amounts about their respectivesupport arm pivot pins 68.

As stated above, each support arm pivot pin 68 is spaced by the commonfixed radial distance R_(f) from the axis of rotation 28. Each supportarm 56 forms a common angle W, shown in FIG. 7, with a line taken alongthe common fixed radial distance R_(f) separating the associated supportarm pivot pin 68 for such support arm 56 from the axis of rotation 28.The common angle W is common to all the support arms 56 because the twosupport arm drivers constrain the proximal support arms 56 a to beoriented at the common angle W, and the rod linkages 62 constrain theremaining support arms to be at the common angle W. The two support armdrivers 90 are operable to change the common angle W by pivoting the twoproximal support arms 56 a about their respective support arm pivot pins68, and the remaining support arms 56 are constrained to pivot togetherby the rod linkages 62. As the support arms 56 are pivoted togetherabout support arm pivot pins 68, the common angle W changes but remainscommon to all the support arms 56. As a result, the forming rolls 54 areconstrained to be a common variable rolling radius from the axis ofrotation 28. The common variable rolling radius is shown as R_(v) inFIG. 7.

The core 22 is supported by a core mount 21, which is operable to rotatethe core 22 about the axis of rotation 28. In the position shown inFIGS. 3 to 5, the core 22 as well as a surrounding layer of a selectedcurable material 24 occupy a cylindrical rolling space defined by theforming rolls 54 to have a radius substantially equal to the commonvariable rolling radius R_(v), less the radius of the forming rolls 54.The core 21 is also pivotable about a pivot axis 30 perpendicular to theaxis of rotation 28, and outside the cylindrical rolling space, suchthat the core 22 can be pivoted into and out of the cylindrical rollingspace.

FIGS. 3, 4, and 5 show the roll forming apparatus 50 in differentpositions, in which the common variable rolling radius R_(v), is changedto define a cylindrical rolling space of varying dimensions. In FIG. 3,the common variable rolling radius R_(v)of the forming rolls 54 from theaxis of rotation 68 is maximized. In this position, the forming rolls 54at the ends of the distal support arms 56 c are spaced from one anotherat a maximum distance, thereby defining a gap 86 through which the core22 can be pivoted into or out of the cylindrical rolling space in whichthe core 22 is centered around the axis of rotation 28.

In FIG. 4, the roll forming apparatus 50 is shown with the support arms56 pivoted about their respective support arm pivot pins 68 by thesupport arm drivers 90 and the rod linkages 62, to reduce the commonvariable rolling radius R_(v), and the dimensions of the cylindricalrolling space. The dimensions of the gap 86 are similarly reduced suchthat the core 22 and the surrounding layer of selected curable material24 will not fit through the gap. In FIG. 5, the roll forming apparatus50 is shown with the support arms 56 pivoted about their respectivesupport arm pivot pins 68 by the support arm drivers 90 and the rodlinkages 62, to reduce the common variable rolling radius and thedimensions of the cylindrical rolling space still further, such that theforming rolls 54 overlap. The features of the forming rolls 54 thatpermit the forming rolls to overlap are shown in FIG. 6.

FIG. 6 shows a sectional view of a forming roll 54. The forming roll 54comprises a small diameter portion 60 and a large diameter portion 58.The large diameter portion 58 is secured to the small diameter portion60 by a radial portion 59. The large diameter portion 58 extends no morethan halfway across the total width provided by the forming roll 54,while the small diameter portion 58 extends across the entire width ofthe forming roll 54, but is partially covered by the large diameterportion 60.

Forming rolls 54 that are adjacent have an opposite configuration inthat the large diameter portions 58 of adjacent forming rolls 54 areoffset from each other so that adjacent forming rolls 54 can overlap.Specifically, the forming rolls 54 supported by the proximal support arm56 a and the distal support arm 56 c of one group of support arms 56 hasthe same configuration as the forming roll 54 supported by theintermediate support arm 56 b of the other group of support arms 56. Theremaining three support arms have the opposite configuration. Thus, thetwo forming rolls 54 at the ends of the two distal support arms 56 c areoppositely configured, such that the large diameter portion 58 of theforming roll 54 mounted on the end of one of the distal support arms 56c is aligned with the small diameter portion 60 of the forming roll 54mounted on the end of the other distal support arm 56 c. As aconsequence of this configuration of the forming rolls 54, the formingrolls 54 are not prevented from being positioned close to one another bytheir large diameter portions 58 as these large diameter portions 58 canoverlap, which permits greater reduction of the common variable rollingradius as shown in FIG. 5, thereby permitting smaller diameterinsulating product to be formed. Preferably, the forming rolls 54 aremade of nickel-plated aluminum in order to maximize rolling hardnesswhile minimizing weight.

The fact that the forming rolls 54 can overlap permits larger diameterforming rolls 54 to be used for rolling smaller diameter insulationproduct then would otherwise be possible. Larger diameter forming rolls54 are preferable to smaller diameter forming rolls as smaller diameterforming rolls provide a correspondingly smaller area of contact with theselected curable material 24. If equal force is provided to the selectedcurable material 24 through smaller forming rolls, this increases thepressure placed on the selected curable material 24, which, in turn,increases the likelihood of fibre damage.

Each of the forming rolls 54 has a coaxial drive sprocket 55 thatengages a roller chain 84 to permit the forming rolls 54 to be driven bythe roller chain 84. The roller chain 84 extends around a path definedby idler sprockets 82 and drive sprockets 88 as well as by the coaxialdrive sprockets 55 of the forming rolls 54. At least one of the idlersprockets 82 is coupled to a tension weight 80 that takes up the slackof the roller chain 84 when the forming rolls 54 are pivoted inwardly asshown in FIG. 5.

Selected curable material 24 is supplied to the core 22 by an inclinedconveyor 74. The inclination of the inclined conveyor 74 is controlledby a conveyor servo-driver 78 (shown in FIG. 4) that automaticallycontrols the inclination of the inclined conveyor 74 to discharge theselected curable material 24 off a discharge end 76 of the inclinedconveyor 74 and onto the core 22 and any selected curable material 24previously deposited onto the core 22. The rate at which selectedcurable material 24 is supplied to the inclined conveyor 74 and fromthere to the core 22 is controlled by a weighing conveyor 70. Therotational speed of the core 22 is controlled by the servomotor 44(shown in FIG. 1), and is based on the weight of the selected curablematerial as measured by the weighing conveyor 70. The rotation speed ofthe core 22 is a function of the feed rate of the selected curablematerial 24 from the inclined conveyor 74 and also of the currentdiameter of the selected curable material 24 formed around the core 22.

As the radial positioning of the forming rolls 54 is not a function ofthe current combined diameter of the core 22 and the selected curablematerial 24 being formed on the core 22, the forming rolls 54 can beadvanced or retracted relative to the current depth of the selectedcurable material 24 on the core 22. Advancing the forming rolls 54 toincrease the forming space will reduce compression of the selectedcurable material 24. Retracting the forming rolls 54 to decrease theforming space will compress the selected curable material 24 as theforming rolls 54 put more pressure on the selected curable material 24.

As the inclination of the inclined conveyor 74, the rate at which theselected curable material 24 is supplied by the inclined conveyor 74,the core rotation speed, and forming roll 54 rotational speed can all beintegrally and precisely controlled, a high degree of control over theforming of the insulation product is possible. Specifically, given alarge ratio of outside diameter of the insulation product to insidediameter of the insulation product, the heat flux at the inside annuluswill be much greater than at the outer circumference. Accordingly,having a higher density at the internal core and a lower density at theouter diameter will provide a higher thermal resistance per unit areathan at the circumference, providing an optimal overall thermalperformance for given total mass of insulation. In order to increase thedensity of the insulation product at the inner annulus, the rotationalspeed of the core 22 can be reduced relative to the rate at whichselected curable material 24 is deposited on the core 22, resulting inmore selected curable material 24 being deposited per unit area. Thenthe cylindrical rolling space can be reduced to compress the selectedcurable material 24, while the rotational speed of the forming rolls 54is reduced to accommodate the slower rotation of the core 22.Accordingly, the fact that all of the foregoing feed characteristic androtational speeds can be precisely and integrally controlled, permits asuperior product to be obtained.

Referring to FIG. 8, there is illustrated a curing oven 110 of a pipeinsulation making apparatus in accordance with a preferred embodiment ofthe invention. The curing oven 110 is operable to cure the selectedcurable material 24 wrapped around the core 22 as shown in FIGS. 1 and2. Curing oven 110 comprises a rear opening (not shown), which is openedand closed by an end door 116, and a main opening (not shown) that isopened and closed by a main door 118.

The curing oven 110 is disposed adjacent to the core support 21 at theside of the curing oven 110 that includes the rear opening and the reardoor 116. In operation, when the main door 118 and the rear door 116 areopened, the core support 21 is operable to pivot the core 22 into thecuring oven 110. The sealing plate 39 of the core support 21 is arrangedto be identical in size to the end door 116 so that it closes and sealsthe rear opening when the core 22 is pivoted into the curing oven 110.The curing oven can then be sealed shut by closing the main door 118using main door cylinders 126 to close the main door 118, and main doorclamps 128 to clamp the main door 118 shut. A seal is maintained by amain door seal 130 when the main door 118 is shut and clamped by maindoor cylinders 126 and main door clamps 128 respectively. A top sealactuated by an air cylinder 122 is brought to bear on the top surface ofthe sealing plate 39 of the core support 21. In the same way, an endseal operated by cylinders 120, and a bottom seal actuated by cylinder124 complete the sealing of the rear opening by the rear door 116 or thesealing plate 39 of the core support 21.

When the core 22 is sealed inside the curing oven 110, curing air, whichhas been heated to above a curing temperature for the selected curablematerial 24, is directed into the oven 110 via the curing inlet 112.Referring to FIGS. 9 and 10, curing air from the oven inlet 112 is firstreceived into a louvered air distribution chamber 132. The louvereddistribution chamber 132 has an elongated slot 134 along the length of aroof 113 of the curing oven 110 adjacent to the main door 118. Theelongated slot 134 distributes the curing air along the length of thecore 22 and the selected curable material 24 wrapped around the core 22.The oven outlet 114 is also disposed on the roof 113 of the curing oven110 but is disposed towards the back side of the oven 110. The placementof the oven outlet 114 and the elongated slot 134 of the louvered airdistribution chamber 132 on opposite sides of the roof of the curingoven induces a rotary curing airflow around the core 22 in the curingoven 110. The airflow rotates around the core 22 in the same directionas the core 22 did when the selected curable material 24 was beingwrapped around the core 22. This rotation of the airflow tightens,rather than loosens, the spooling of the wound selected curable material24 on the core 22.

The fact that the oven 110 is sealed enables a positive pressure to bebuilt up within the oven 110. At the same time, as described above inconnection with the description of the core 22, a partial vacuum ismaintained within the core 22 by airflow through the vacuum conduit 32and vacuum exhaust duct 34. The combination of the positive pressurewithin the oven 110 and the partial vacuum within the core 22, generatesa significant hot or curing air static pressure across the selectedcurable material 24 wrapped around the core 22. The resulting flow ofcuring air through the selected curable material 24 and the perforations26 of the core 22 maintain the selected curable material 24 in thecompressed configuration effected during forming by preventing expansionof the selected curable material 24 and also provides effective heattransfer due to the velocity of hot air passing through the selectedcurable material 24. The compression of the selected curable material 24under vacuum is maintained until the selected curable material 24 iscured, in order to maintain the desired compression. The oven 110 iskept as small as possible while still accommodating the core 22 and theselected curable material 24 wrapped therearound, in order to permit theselected curable material 24 to be cured as rapidly as possible.

By closing end door 116 and main door 118, the curing oven 110 can bepreheated prior to receiving the core 22. Once the oven 110 has beenpreheated, a bypass valve 172 can be switched in conjunction with a hotair supply valve 170 and an oven pre-heat return valve 176 being closedto allow the air to bypass the oven 110 entirely. This allows the enddoor 116 and the main door 118 of the oven 110 to be opened and for thecore support 21 to pivot the core 22 into the curing position within theoven 110, at which point the main door 118 of the curing oven 110 can beclosed to seal the core 22 within the oven 110. The sealing plate 39 ofthe core support 21 seals the rear opening of the oven 110 shut.

The above-described structure of the oven 110 also permitsself-cleaning. In order for the oven 110 to self-clean, an empty coremoves into the oven 110 and hot air that is heated to above the normaloperating temperature is ducted into the curing oven 110 via the oveninlet 112 and the elongated slot 134 of the louvered air distributionchamber 132. This high temperature cleans the interior of the oven 110and the ducts without requiring the ducts to be dismantled, therebyimproving the availability and economics of the apparatus.

Referring to FIG. 11, there is illustrated a preferred layout of a pipeinsulation making apparatus in accordance with a preferred embodiment ofthe invention. As shown in FIG. 11, the pipe insulation making apparatusaccording to the preferred layout includes two cores 22 and two ovens110. Each of the two cores 22 is supported by separate core supports 21.The core supports 21 pivot the cores 22 from a single forming position,designated 22 a in FIG. 11, in which the selected curable materialaround each of the two cores 22 is formed by the roll forming apparatus50 at different times. The core supports 21 are spaced on each side ofthe forming station. After forming, each core 22 is pivoted 180 degrees,through an intermediate position at 90 degrees designated 22 b in thedrawings, to a curing position 22 c within the curing ovens 110.

Referring to FIGS. 12 to 15, there are illustrated different portions ofa duct system of a pipe insulation making apparatus in accordance with apreferred embodiment of the invention. The duct system is operable toprovide forming airflow to both of the vacuum cores 22 during forming,and to provide curing airflow to both of the ovens 110 and both of thecores 22 during curing in accordance with the preferred embodiment ofthe invention. FIGS. 12 and 13 in different cut-away plan views,illustrate mainly those portions of the duct system 135 that provide thecuring airflow to the ovens 110 and the cores 22 during curing. FIG. 14,in a further cut-away plan view, illustrates mainly those portions ofthe duct system 135 that draw the forming airflow from the cores 22during forming. FIG. 15 is a cut-away perspective view of the ductsystem.

Each of the core supports is adjacent to a different curing oven 110;each curing oven 110 is positioned to be on the opposite side of theadjacent core support 21 from the forming station. When the selectedcurable material 24 has been fully formed at the forming station, thecore support 21 pivots the core 22 through 180° C. and into the adjacentoven 110, at which point the sealing plate 39 of the core support 21will seal the end opening of the adjacent oven 110. The main door 118then closes to seal the core 22 and the formed selected curable material24 wrapped around the core 22 into the curing oven 110 for curing. Theforming station is then free for the other core 22 to be pivoted intoposition in the forming station to receive and form new selected curablematerial 24.

The partial vacuum within each core 22 and the positive pressure withineach oven 110 during curing are maintained by hot air recirculation fans140. The hot air recirculation fans 140 force hot curing air into thecombustion box 142 via recirculation outlet lines 154. In the combustionbox 142, the hot curing air is heated to a temperature above the curingtemperature for the selected curable material 24. The positive pressuregenerated by the hot air recirculation fan 140 forces the heated curingair out of the combustion box 142 and into the hot air recirculationlines 144. Each of the hot air recirculation lines 144 communicates withdifferent oven inlets 112 such that heated curing air is discharged intoeach oven 110 via its oven inlet 112, louvered air distribution chamber132, and elongated slot 134. A minimal amount of curing air isdischarged from each oven 110 into oven hot air outlet lines 150. Apartial vacuum is maintained in oven hot air outlet lines 150 by the hotair recirculation fans 140 in order to draw some small portion of thecuring air out of the ovens 110 and into the oven hot air outlet lines150. The oven hot air outlet lines 150 are connected to the hot airrecirculation fans 140 such that the curing air from the oven hot airoutlet lines 150 is redirected to the combustion box 142 via the hot airrecirculation fans 140 and the recirculation outlet lines 154. Most ofthe heated curing air that is released into each oven 110 via its oveninlet 112 is drawn through the selected curable material 24 and into thecores 22 via the perforations 26. The spent curing air within the cores22 is then drawn back to the recirculation fans via turret outlet lines152. The hot air recirculation lines 154 then channel this air, togetherwith the curing air received from the oven hot air outlet lines 150,back to the combustion box 142.

As described above in connection with the description of the curing oven110 shown in FIG. 8, duct system 135 includes a bypass valve 172 foreach curing oven 110 for redirecting all the heated curing air in thehot air recirculation lines 144 into oven hot air outlet lines 150 viaoven bypass lines 148, without this curing air passing through the ovens110, when each core 22 is being pivoted into its oven 110 afterpreheating of the oven 110. To facilitate this, the hot air supplyvalves 170 in the hot air recirculation lines 144 and the oven pre-heatreturn valves 176 in the hot air outlet lines 150 are also closed. Thebypass valves 172 will remain partially open during the cure cycle tomaximize the fan static pressure built up within the ovens 110.

After the selected curable material 24 has been cured, it must becooled. Preferably, air that has been used to cool the selected curablematerial 24 after curing is used as input air into the ducting system135 in order to retain the heat absorbed by this cooling air duringcooling of the selected curable material 24. Referring to FIGS. 13 and15, cooler air outlet line 158 communicates with both turret hot airoutlet lines 150. Air from cooler air outlet line 158 is drawn back tohot air recirculation fans 140. This air is then sent along with spentcuring air to the combustion box 142 via the recirculation outlet lines154 for heating and incineration removal of the smokes obtained from theselected curable material 24. The cooler air outlet line 158 has acooler return valve 174 that is a variable valve and serves to limit thevolume and maximize the heat recovery from the air flow from the cooleras well as permitting optimal incineration.

As shown in FIG. 12, a cooler discharge line 162 for discharging excesscooling air includes a cooler discharge valve 180. Preferably, coolingair that cannot be returned to the hot air recirculation system in theabove-described manner, is filtered before discharge in order to removethe smokes obtained from the selected curable material 24 during curing.Exhaust from the combustion fuel used to maintain the temperature incombustion box 142 is discharged via exhaust stack line 156 through avariable exhaust valve 182 (shown in FIG. 12) that serves to optimizesystem pressure and flow.

Referring to FIGS. 14 and 15, the cold air duct work of the duct system135 is illustrated. As shown in the plan view of FIG. 14, forming airfan 164 generates a partial vacuum in turret cold air outlet lines 160.Turret cold air lines 160 communicate with cores 22 via vacuum exhaustducts 34 and vacuum ducts 32 to maintain a partial vacuum in theinterior of the cores 22. Hot core suction valves 178 in turret hot airoutlet lines 152 are closed and cold core suction valves 184 in turretcold air outlet lines 160 are open to direct the forming air flow intothe cold air outlet lines 160.

Referring to FIG. 15, there is illustrated a cut-away perspective viewof the duct system 135. The vacuum exhaust duct 34 of each of the twocore supports 21 leads to a juncture of one turret hot air outlet line152 and one turret cold air outlet line 160. During curing, the turrethot air outlet line 152 is connected to the vacuum exhaust duct 34,while during forming, the turret cold air outlet line 160 is connectedto the vacuum exhaust duct 34. Turret cold air outlet line 160 leads toforming air fan 164, which provides the partial vacuum in turret coldair outlet 160, vacuum exhaust duct 34, vacuum duct 32 and the inside ofcore 22. From the forming air fan 164, the spent forming air isdischarged through a cold air exhaust conduit 166 to a suitable filtersystem. The turret hot air outlet lines 152 lead to the hot airrecirculation fans 140, as do the oven hot air outlet lines 150. Fromthe hot air recirculation fans 140, curing air is redirected to therecirculation outlet lines 154 and from there to the combustion box 142and the hot air recirculation line 144 as described above.

Other variations and modifications are possible. All such modificationsor variations are believed to be within the scope of the invention asdefined by the claims appended hereto.

What is claimed is:
 1. An apparatus for receiving a selected curablematerial and for retaining the selected curable material during aforming stage and a curing stage, the selected curable material beingformed into a desired configuration during the forming stage and beingheated during the curing stage to harden the selected material in thedesired configuration, the apparatus comprising: a core mounted forrotation about an axis of rotation, the core having an associated corerotation means for rotating the core about an axis of rotation, an outerpermeable surface for receiving and retaining the selected curablematerial, and fluid communication means for receiving air flow from theouter permeable surface; a curing means for heating the selected curablematerial to at least a curing temperature to harden the selected curablematerial in the selected configuration, wherein the curing meansincludes a curing station for supplying a curing air supply around thecore, and air heating means for heating the curing air supply to atleast the curing temperature; and, the vacuum means includes a formingair outlet for receiving the forming core air flow from the fluidcommunication means, a recirculation outlet for receiving the curingcore air flow from the fluid communication means and for recirculatingthe curing core air flow back to the curing station, and a valve meansfor controlling fluid communication between the forming air outlet andthe fluid communication means and for controlling fluid communicationbetween the recirculation outlet and the fluid communication means; and,a vacuum means in fluid communication with the fluid communications ofthe core for drawing a forming core air flow through the fluidcommunication means, the outer permeable surface of the core and theselected curable material retained on the core during forming of theselected curable material retained on the core, the forming core airflow having a temperature below the curing temperature, and drawing acuring core air flow through the outer permeable surface and the fluidcommunication means of the core and the selected curable materialretained on the core during curing of the selected curable materialretained on the core.
 2. The apparatus as defined in claim 1 wherein thevacuum means includes an exhaust fan for discharging the forming coreair flow via the forming air outlet; and, a recirculation fan forrecirculating the curing core air flow to the curing station via therecirculation outlet.
 3. The apparatus as defined in claim 1 wherein thevalve means has an associated forming setting, the valve means in theassociated forming setting being operable to connect the forming airoutlet to the fluid communication means, and to disconnect therecirculation air outlet from the fluid communication means; anassociated curing setting, the valve means in the associated curingsetting being operable to connect the recirculation air outlet to thefluid communication means, and to disconnect the forming air outlet fromthe fluid communication means; and, an associated distributed settingbetween the associated forming setting and the associated curing settingfor providing continuous air flow through the core when the apparatus ischanging from the forming stage to the curing stage, the valve meansbeing operable to decrease fluid communication between the forming airoutlet and the fluid communication means and to conjointly andproportionately increase fluid communication between the recirculationair outlet and the fluid communication means when the valve means ismoving through the associated distributed setting from the associatedforming setting to the associated curing setting.
 4. The apparatus asdefined in claim 3 further comprising a forming station for forming theselected curable material retained on the core into the selectedconfiguration; and, a core support for supporting the core, the coresupport being pivotable about a pivot axis to pivot the core between theforming station and the curing station, the core support having a vacuumconduit for providing fluid communication from the fluid communicationmeans of the core to the forming air outlet and the recirculationoutlet, the valve means being operable to control fluid communicationbetween the forming air outlet and the vacuum conduit and to controlfluid communication between the recirculation outlet and the vacuumconduit.
 5. The apparatus as defined in claim 4 wherein the curingstation comprises a curing oven for receiving the core and for supplyingthe curing core air flow to the core, the core support being operable topivot the core into and out of the curing oven.
 6. The apparatus asdefined in claim 5 wherein the curing oven has a rear opening, a mainopening and a main door for closing and opening the main opening, themain opening extending lengthwise along the curing oven and the coresupport being operable to pivot the core into and out of the curing ovencore when the main door is open; the core support is positioned besidethe rear opening of the curing oven and has a sealing plate dimensionedto close and seal the rear opening of the curing oven when the core ispivoted into the curing oven when the main door of the oven is open, themain door being closeable when the core is in the oven to seal the coreand the selected material retained thereon in the oven for curing. 7.The apparatus as defined in claim 6 wherein the curing oven comprises acuring air inlet for discharging the curing air supply into the curingoven, the curing air inlet being in fluid communication with therecirculation outlet; and the air heating means is between therecirculation outlet and the curing air inlet to heat the curing airsupply to at least the curing temperature.
 8. The apparatus as definedin claim 7 wherein the curing oven includes a rear door for closing therear opening, and the curing air inlet includes an associated bypassvalve for disconnecting the curing air inlet from the curing oven andrerouting the curing air supply back to the air heating means.
 9. Theapparatus as defined in claim 7 wherein the curing oven includes an ovenair outlet for drawing an oven air outflow from the curing oven and forinducing a rotational air flow of the curing air supply around the corein the curing oven, the oven air outlet being in fluid communicationwith the air heating means and the curing air inlet to recirculate theoven air outflow back to the curing air inlet after the oven air outflowhas been reheated; and, the oven air outlet and the curing air inlet arelocated on a common side of the curing oven and are disposed on oppositesides of the core.
 10. The apparatus as defined in claim 9 wherein thecuring air inlet extends lengthwise along the common side and releasesthe curing air supply along substantially an entire length of theselected curable material retained on the core.